Are you shy or an extrovert? A risk-taker or a cautious soul?

Are you shy or an extrovert? A risk-taker or a cautious soul? Are you fat, thin, tall, short? An athlete or a couch potato? Whatever your characteristics, can you put it down to your genes? An event next week will give you the chance to find out. KAY JORDAN reports

For many, boarding a plane for their summer holiday is enough to make them break out in a cold sweat.

Ian Rosenvinge actually makes his living jumping out of one. The former Army major, of Newton Hall, Durham City, is a risk taker and veteran of 3,000 jumps.

Ian, 45, who runs the Peterlee Parachute Centre, has always been an action man. As a boy he did the customary climbing of trees and rocks but as he got older he knew he wanted adventure, which is why he sought an Army career.

Even on leave he wanted to stretch himself to the limits, which led him to try everything from potholing and mountain climbing to canoeing.

His scariest moment came canoeing.

"I went upside down near a weir and I forgot to release the spray deck which holds you in. It was frightening trying to get my head above the water. "

He also tried freefall parachuting and as a result went to a parachute unit after doing his military training at Sandhurst and ended up running the Army parachute team.

Even with all his experience, he says he still feels apprehensive as a jump approaches although, parachuting is not as risky as most people think.

"It is relatively safe; it's less dangerous than horse riding. Of those doing their first jump, six in 1,000 will be injured and that may just be a sprained ankle or a broken toe. But there is always the fear that you could be killed and if there wasn't this perceived risk people wouldn't do it.

"You get an incredible adrenaline rush when you've overcome your apprehension and jumped."

Because he's now a family man, with daughters aged three and three months, he says he looks at the risk differently when he jumps.

"There's not just myself to think about if anything goes wrong - there's my wife and my two children."

The biggest buzz, in jumping now is when he does accelerated freefall, with beginners.

"Basically, there's an instructor holding on to them on either side, acting as stabilisers, and we can tap them on the head or give them hand signals to tell them what they need to do but the buzz comes as you don't know what they're going to do. They could forget to pull the ripcord." Ian doesn't know if risk-taking is in his genes but his 78-year-old father would love to do a jump with him - if only Ian's mum would let him!

So, is Ian programmed to seek that adrenaline rush?

Professor John Burn, medical director of the Genetics Institute at Newcastle's Centre for Life, says it's not a question of a simple gene for traits such as risk-taking.

"Almost no gene is that determinant, although clearly there are exceptions in terms of health."

Otherwise, genes and how they influence our behaviour are inter-related with our environment, he says.

"I draw the analogy of the wheels of a bike. Which is more important, front or back? The answer is a bike needs both wheels to work.

"You can't say because your dad drove a sports car that you will drive a sports car but the environment factor is there. Maybe you will decide you want to prove you are like your dad.

"It's much more complicated a decision process than saying you've got a gene and you can't avoid it."

Prof Burn will be at an open house on the subject on genetics at Life Interactive World, at the Centre for Life, on Wednesday, organised as part of the BBC's Gene Stories season.

Researchers turned to him for advice when making the series, How to Build a Human, which told the story of how humans are made, and Threads of Life, which described cells, strands of DNA, human eggs and cloning.

The topic of twins is likely to come up for discussion on Wednesday, since twins are crucial to genetic research.

As Prof Burn points out, for 100 years now it has been known that identical twins share the same set of genes.

"If you look at any disease and compare identical and non-identical twins, if it is genetic you should see a difference between them," he explains.

Do you feel each other's pain? Are you telepathic? Do you know what the other is thinking? These are questions she and twin sister Caroline, a journalist, are always asked. Their usual answer, says Kelly, of Dunston, Gateshead, is a weary no.

"Yet the more I think about it, I am inclined to answer with a cautious yes.

"I don't collapse in agony every time she stubs a toe, nor do I have an internal running commentary on her life but when it comes to her, there are many things that I just know.

"While I don't feel her physical pain, I feel her emotional pain. I can tell what she is thinking by a look on her face, the tone of her voice, the flick of an eyebrow. I can read her like a book."

Shop assistant Kelly, 25, doesn't believe there's anything supernatural about it - just that she knows her sister well.

"We share the same genes, grew up in the same environment, with the same friends and experiences.

"The only vaguely telepathic thing I can think of is one day I was about to fall asleep and I felt myself wake up and say Caroline is going to ring. The phone rang and it was her."

Their relationship is like no other in her life, she says. "It's not like you would have with an ordinary sister or a best friend. It is very intense."

She feels society wants twins to be alike and share all manner of connections but, in reality, many are fighting a constant battle to assert their individuality.

"I don't believe people truly understand the value of individuality. I do because, in the eyes of society, I'm one of a pair.

"When I was young the thought of being an identical twin was fantastic. We could play tricks on people, be the centre of attention and everyone knew us. But that changed at adolescence.

"If Caroline wore trousers, I wore a skirt. She cut her hair short and dyed it jet black, I wore mine long and fair. Like most adolescents, I was trying to find out who I was but with the added complication of being with someone just like me."

Friends describe them as chalk and cheese, she says, although they've always shared the same talents.

"We were very sporty in our younger days but I always seemed to have the athletic edge. She was always the more talented artist.

"Caroline has always been very focused on her career and knew what she wanted from a young age. I have a tendency to sail through life. This is why the most startling difference between us today is our pay!"

Being a twin will always mean she has a best friend and confidante who she knows and trusts implicitly. Kelly adds: "We share everything - except the same taste in men - and are there for each other no matter what. But the best thing about having a double is twice the amount of clothes."